The MASCA Project was a follow-up of the RASPLAV Project and investigated in-vessel phenomena during a severe accident. In particular, it addressed the influence of the chemical composition of the molten corium on the heat transfer to the pressure vessel environment. The project addressed this by investigating stratification phenomena of the molten pool and the partitioning of fission products (FP) within the different layers of the melt. The project was scheduled to be completed in July 2003, but it was continued until 2006 under the MACS-2 Project, given the experimental needs that still exist and the quality of the experimental work done so far.

The tests aimed to resolve remaining uncertainties about the heat load on the reactor vessel and thus the possibility of retaining the melt in the vessel. These uncertainties are mainly associated with scaling effects and coupling between the thermal-hydraulic and chemical behaviour of the melt. Supporting experiments and analyses - in addition to helping understand key in-vessel phenomena - facilitated a consistent interpretation of the results. The experiments were carried out with corium compositions prototypical of power reactors which use iron and steel materials. The MASCA experimental goal was achieved through corium tests of different scale, and was complemented by pre- and post-test analyses and development of computational models. Additional measurements of thermo-physical properties of the melts such as density, thermal conductivity and liquidus-solidus temperatures considerably expanded the material properties data obtained during the RASPLAV Project.

The major goals of the MASCA Project were to:

Investigate the influence of chemical behaviour on heat transfer in stratified molten pools of prototypical compositions;

Investigate FP behaviour in a molten pool and in particular:

Partitioning of FP between layers in case of stratification;

Partitioning of FP between phases during melting and solidification;

Distribution of FP simulants in the melts.

Expand the material properties database;

Develop computer models describing the relevant phenomena.

Separate effects were studied in series of small- and mid-scale experiments. Corium tests were performed in the RASPLAV, TULPAN, TF, STF, KORPUS, and TIGEL facilities. Salt tests were performed in the present RASPLAV-Salt facility.